• Oct 29th 2007, 08:57 AM
JBswe
The amount of a radioactive preporation y mg decreases by the formula
y=80*0.5^0.2t where t is the time in years after the start of 2000, what is the average rate of change between the start of 2005 and the start of 2007

I know am suppose to put the years into the calculation some place but from there am lost
• Oct 29th 2007, 10:44 AM
Jhevon
Quote:

Originally Posted by JBswe
The amount of a radioactive preporation y mg decreases by the formula
y=80*0.5^0.2t where t is the time in years after the start of 2000, what is the average rate of change between the start of 2005 and the start of 2007

I know am suppose to put the years into the calculation some place but from there am lost

the average rate of change for $y(t)$ from 2005 to 2007 is given by: $y_{avg}(t) = \frac {y(7) - y(5)}{7 - 5}$

can you continue?
• Oct 29th 2007, 12:57 PM
JBswe
ok tryed to work it , is the answer 10.31mg?
• Oct 29th 2007, 01:14 PM
Jhevon
Quote:

Originally Posted by JBswe
ok tryed to work it , is the answer 10.31mg?

i got a negative answer (which you should, since the sample is decreasing)